a) Electron microscopic-immunocytochemical identification of growth hormone and prolactin cells will be sought in normal and neoplastic human hypophysial tissue removed at autopsy or during surgery. b) The cyclic AMP-sensitive protein kinase of goitrous rat thyroids will be compared with that from normal tissue, in search of possible qualitative differences. c) Iodotyrosine deiodination in rat thyroid lobes will be studied with regard to 1) kinetics, with MIT and NADPH as substrates, 2) the effect of TSH and iodine binding on it, and 3) comparison of iodide of deiodination with transported iodide as far as availability for organic binding is concerned.